feat(eval): add field-level OCR accuracy harness + seed corpus

Adds a measurement gate for the artifact OCR parser (ADR-007), the prerequisite
for the layout-profile and preprocessing rework. runOcrEval feeds labeled OCR
text through the real parseArtifactCandidate and scores per-field / per-case
accuracy.

- src/eval/ocrEvalHarness.ts: pure metrics (per-field, critical-field, exact).
- src/eval/corpus/seedCorpus.ts: 23 cases transcribed from the verified parser
  test assertions; runs at 100%.
- src/eval/reviewSampleCorpus.ts: converts review samples into label *candidates*
  (never ground truth) so the review queue can grow the corpus.
- src/eval/ocrEval.test.ts + reviewSampleCorpus.test.ts: gate (must stay 1.0) and
  converter unit tests.
- npm run eval script; docs/ocr-eval.md; ADR-007/008/009.

Also records the agreed rework direction: C# input/capture sidecar (ADR-008) and
resolution-anchored layout profiles + OCR preprocessing (ADR-009).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -14,6 +14,7 @@
     "start": "electron .",
     "lint": "tsc --noEmit",
     "test": "vitest run",
+    "eval": "vitest run src/eval/ocrEval.test.ts",
     "data:genshin": "node scripts/generate-genshin-data.cjs"
   },
   "dependencies": {